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Is altitude all that it ‘seams’?

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Colorado Rockies news and links for Tuesday, December 28, 2021

As long as MLB’s official baseballs are hand-stitched, they won’t be 100% identical.

This presents a problem for the meticulous data collection in this game. We can’t expect all pitch data to be 100% accurate if the baseball itself is inconsistent.

It’s safe to reason that no two baseballs will be identical — which might be a good thing, if differences can help combat the drastic effects of baseball at elevation.

Send the baseballs with higher drag to Denver.

Barton Smith is a mechanical and aerospace engineering professor at Utah State University, and is know in baseball circles as the “seam tamer” as mentioned on his Twitter account. Smith’s research on baseball flight has served as a backbone for discussions on seam-shifted wake and laminar flow, among other topics, and he’s previously determined the variation in seam height with official big league baseballs. Seam height is often far from uniform.

In 2019, Smith found a variance range for MLB seam height, ranging from 0.025 to 0.039 inches in the large sample he worked with.

A 2019 MLB study showed that seam height contributed to a spike in home runs. From the study: “The committee of scientists determined a drop in the average seam height of less than 0.001 inches was responsible for 35 percent of the decrease in drag on the ball.”

Less than 0.001 inches was responsible for 35 percent of drag decrease.

A 0.014-inch range is a problem.

The humidor at Coors Field can help make baseballs more consistent, but it won’t adjust the seams like it adjusts for moisture. Every park could use a seam-sizing equivalent to the humidor in the modern era.

Let’s head to the Rawlings factory

From How It’s Made (Discovery Channel):

If we assume Rawlings hasn’t changed their MLB assembly line since this video was published, this is how seams are regulated. A rolling mechanism sets baseball seam height around the 4 12 minute mark. This is where stitches are smoothed down to MLB regulation height, but unless each baseball rolls through this machine exactly the same, it is a source of variance — and a source for where we might be able to pick out high-elevation baseballs.

If we rewind back to the stitching process, we can wonder just how uniform all 108 stitches are on a hand-stitched baseball.

  • One baseball ‘stitcher’ may pull at the threads a little tighter than another.
  • The first baseball of the day will likely be stitched a little differently than the final one, if fatigue is accounted for.
  • Maybe the thread is a hair thicker on a given day.
  • The factory might have been in a rainstorm the night before and the thread might retain a little more moisture
  • *insert more variables here*

Each baseball is subject to rigorous quality testing, but the Hawkeye data at each MLB ballpark is a lot more precise than the construction of the baseballs themselves. If each ballpark can track every blade of grass in play, how much is the data thrown off by an irregular seam?

An altitude adjustment

Maybe we don’t need a 100% consistent baseball. Maybe we need exactly what we have right now — but an advanced sorting process to send the balls where they belong.

Aerospace engineer (and Lakewood, Colorado’s own) Josh Stamps had a Twitter discourse with Barton Smith on this exact topic:

Smith went on to add that “the relationship between drag and air density (and altitude) is linear, while drag and seam height may not be.” He also said that having “Denver balls” is a great idea, which is the source of this article’s inspiration.

The deep end: High elevation baseballs?

High-elevation tennis balls exist. Why doesn’t baseball follow suit?

Tennis balls are filled with air, and it’s relatively easy for a manufacturer to adjust the pressure inside of them for play above sea level. It would take a lot more insight to develop new cork and new twine for baseballs to follow suit, but it doesn’t mean it isn’t possible.

Starting in 2011, the NCAA changed the way it governed its metal bats. The former BESR certification (Ball Exit Speed Ratio) was replaced with BBCOR certification (Batted Ball Coefficient of Restitution), and the dead ball era of college baseball ensued — that is, until the NCAA recognized how big of a switch it was.

In 2015, a new baseball was put in play for college games to see more action at the plate again.

This is not a new prophecy in the big leagues: MLB changed baseballs before the 2021 season too.

If MLB can reverse-engineer some BBCOR certifications for the baseball itself, we could soon see new balls in play for high-elevation action, which could help control against the additional distance that home runs carry in Denver. Perhaps we could even see a new stamp on the balls to designate them for appropriate high-elevation use.

(Just lace them with purple seams for us.)

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